Beaula McCalla, a youth worker from the UK town of Bristol, never imagined that she would one day meet her relatives in Equatorial Guinea, 6,500 km away.

"It was like blood touching blood... It was like family," she said.

Beaula, an African-Caribbean descendent of slaves, was reunited with her long-lost family thanks to a unique genetic study undertaken for a BBC programme, Motherland: A Genetic Journey.

A romantic ideal I had was shattered

Mark, a Kanuri from London

She says that she always thought of herself as an African but now she has the genetic proof, some 200 years, or 11 generations, after her ancestors were captured, taken across the Atlantic Ocean and made to work as slaves.

Tests showed that some of her ancestors were from the Bubi ethnic group, which live on the Equatorial Guinea island of Bioko.

In the village of Moka, eight people were found to have a common maternal ancestor with Beaula.

They welcomed her with open arms and gave her a piece of land.

"I was just crying, my eyes were just filled with tears, my heart was pounding. All I just kept thinking was: 'I'm going to my motherland,'" she said about her arrival in Equatorial Guinea.

For the first time since the enslavement of their African ancestors and the eradication of their ethnic identities, advances in DNA analysis have now made it possible for individuals to discover from which African region or population group their families originated.

The study, the most comprehensive attempt so far to investigate the specific roots of the descendants of slaves, took anonymous DNA samples via a swab from inside the cheeks of 229 volunteers (109 men and 120 women).

The only criterion for all volunteers was that they had four African-Caribbean grandparents.

The universities of Cambridge and Leicester in the UK and Pennsylvania State in the United States analysed the DNA.

'Homecoming'

Mark Anderson, from south London, discovered that he has blood from the ethnic Kanuris who live in south-eastern Niger.

He was surprised to find his distant relatives living among the sand dunes of the Sahara desert, having imagined Africa to be full of lush forest.

Mark was surprised to find a desert in Africa

After this initial shock, he too had an emotional "homecoming" and chose a Kanuri name - Kaigama.

However, he later discovered that this was the name of a Kanuri slave-trader who captured and sold his kinsmen.

"A romantic ideal I had was shattered," he said. "This is a complex story."

In contrast, Jacqueline Harriott, a Peterborough schoolteacher, felt no connection with Africa and was pleased to discover that genetically, she is 28% European.

As well as individual ancestral profiles, the Motherland study also quantifies, for the first time, one of the most sensitive genetic legacies of the Transatlantic slave trade; the extent to which African female slaves were made pregnant by European slave-owners.

The study reveals that more than one in four British African-Caribbeans have white male ancestry on their direct father line.

Analysis showed that 27% of British African-Caribbean men have a Y chromosome (passed directly from father to son) that traces back to Europe, not Africa.

The autosomal study, investigating DNA inherited from all an individual's ancestors, demonstrated that on average, more than one in seven (13%) ancestors of today's Black Britons of Caribbean descent would be of European origin.

The BBC Documentary Motherland: A Genetic Journey will be broadcast on BBC 2 at 9pm on 14 February